#!/user/bin/env node

//console.log(process.argv);

//console.log(process.argv[2],'\n', process.argv[3]);

const arg = process.argv[2],
      log = console.log;

if(typeof(arg) === 'undefined' || arg === '--help' || arg === '-h'){
  help();
}else{
  calc();
}

function help(){
  log('\
      usage:cmd-name [OPTION] [expression]\n\
      evaluate the expression.\n\
      \n\
      Mandatory arguments to long options are mandatory for short options too.\n\
      -h,--help output help information and exit');
}

function calc(){
  try{
    log(`${arg} = ${eval(arg)}`);
  }catch(e){
    console.error(`${arg}不是合法的数学表达式！`);
  }
}



